Generally, information repositories hold a wealth and variety of information that can be accessed. Examples of information repositories include program files comprising a list of subroutines and/or variables used in the program, and databases comprising records. Information repositories can also be in non-automated form, such as library index cards comprising information like call numbers, publishers, and authors. In a small information repository, information can be relatively easy to decipher and organize. As is often the case, however, any useful information repository will contain and accumulate an infinite amount of information so that organizing the information in any useful manner becomes a difficult task. This problem can be demonstrated in an information repository such as a database.
Databases are a large and powerful resource of information in a society automated by computers and computer processes. A database is a repository of files containing records, where each record contains fields that are attributes of the record, and every record in the same file comprises the same fields. For example, records in a job database can comprise fields such as Position, Level, Company, Salary, Years of Experience, and Skills, each of which is an attribute of a job in the job database. In a more general sense, a database is also a collection of files containing records that are subject to the same set of operations for searching, sorting, recombining, and other functions.
Information in a database can be accessed by a custom program written for a particular application. For example, a program in a job placement application might display a list of all available jobs from a job database. This method of access to database information is limited, however, because it requires that such a program be customized for a particular use, language, and/or database, amongst other factors, which can involve a great deal of expertise, time, and expense. While this is oftentimes necessary, particularly where a database is highly integrated into an application and a user needs sophisticated functionality such as the ability to add, change, and delete database records, it can be overkill for a user who needs minimal access, such as when the user only needs to view database records.
For minimal use, a database can also be accessed by "querying" the database, which at the very least does not require the expertise, time, and expense of a custom program. A query is a specific set of instructions for the purpose of extracting data from a database based on one or more selection criterion. For example, if a user wants to see all jobs in a job database that pay more than $20,000, a query might read "(Salary&gt;=$20,000)". The query, which is written in commands comprehensible by the particular database being queried (eg., SQL), instructs a program to search the database for any and all records that satisfy the one or more selection criterion of the query. In the previous example, therefore, a program reads the Salary field of each record to determine if the value in that field is greater than or equal to $20,000. If the test fails, the program proceeds to test the next record. If the test passes, the program will extract that record from the database for processing, such as viewing or displaying. The result is a cost effective method of extracting information from a database tailored to a user's specific needs.
While creating queries is cost effective, it is not always efficient. Oftentimes, a user needs access to a specific set of records that requires a more complex query, such as when a user wants to see all of the available professional jobs that do not require computer programming skills. A query to obtain this information from a database might read "((isAvailable=TRUE) AND (Tech/Prof=TRUE) AND (skills&lt;&gt;computer) AND (job&lt;&gt;programmer))". In a complex query, such as this one, the results can sometimes be uncertain, requiring the user to make several attempts at creating the query to produce the correct results. Another disadvantage of queries, simple or complex, is that they can result in wasted time and space in obtaining commonly used data, and in creating a litany of queries which produce the same results and/or erroneous results.
A need exists, therefore, for meaningful and easy access to information in an information repository that provides the detail of information available from a custom program without the time and expense of creating one, as well as the cost-effectiveness of querying an information repository without the uncertainties of results and the inefficiencies in obtaining them. In a more general sense, a need also exists for a means of meaningful and easy access to information an information repository that presents a user with a conceptual view of the information repository.